Patent GB-111849-A (GB)
Title: Improvements in Electric Motor Control Systems.
IPC: H02P7/34
Filed: 1917-11-22
Abstract: 111,849. British Westinghouse Electric & Manufacturing Co., (Assignees of Hanff, E. A.). Nov. 22, 1916, [Convention date]. Systems for continuouscurrent motors only.-In a regenerative control system the motor and generator armatures, connected in a closed circuit and having separately excited fi e l d windings, relays are provided automatically to vary the resistances in the respective field circuits when an excessive current traverses the main circuit, and a reverse current relay reverses the operation of the resistance relays when the motor is acting as a generator. A motor 4 supplied from mains 1, 2, 3 drives the generator G and the common shaft of the machines carries a flywheel 5. An electro-magnetic switch 6 cuts resistance into the rotor circuit of the motor 4 when the current supplied to the motor exceeds a predetermined value. The armatures of the working motor M and the generator G are permanently connected together, the circuit including the windings of vibrating relays 15, 28 and the winding 31 of the reverse current relay 30. The machines are excited from constant voltage mains 36, 38, the generator field 8 being supplied through variable resistances 9 and the motor field 19 through resistances 20, 48. One section of the generator field resistance 9 is controlled by the relay 14 subject to the action of the relay 15 and the section 48 of the motor field resistance is similarly controlled by the relays 46, 28. The whole of resistance 20 is short circuited by the relay 21 when the controller 35 is in its zero position or in positions a - - e. To start the forward motion of the motor M the controller is moved to the position a. This causes the reversing switch 16 to close the generator field circuit through all the resistance 9 except the section short-circuited by the relay 14. The switch 34 also closes to connect the shunt coil 32 of relay 30 in circuit so that the coils 31, 32 are opposed. At this stage the generator field is weak and the motor field strong, and during the movement of the controller through the positions b, c, d, e, the relays 10, 11, 12, 13 are operated to short circuit the resistance 9 and strengthen the generator field. The controller may be moved directly from zero to position e and the relays 10 - - 13 then operate in order, but if the main current rises to an excessive value the vibrating relay 15 acts to cause the relay 14 to open to insert a section of resistance in the generator field circuit. As the controller is moved towards its final position the relays 21 - - 26 are operated to cut resistance into the motor field circuit subject to the action of the relay 27 controlled by the vibrating relay 28. During braking, with the controller in its zero position, the motor field strengthened and the generator field weakened, the current in the main circuit is reversed and the relay 30 is lifted. The machine M acts as generator and in the event of an excessive current flowing in the main circuit the relay 28 causes the switch 46 to open to insert resistance into the circuit of the field 19. The relay 15 causes the relay 14 to cut out resistance from the circuit of the field winding 8. In a modification an electro-magnetic switch controls a shunt circuit for the larger portion of the resistance 9 and can only be energized when the relays 15, 30 are raised.